Assessments of severe behavior disorders of children with intellectual and developmental disabilities (IDD) have revealed that behavior problems are often maintained by their functional outcomes (or reinforcers). For example, children may gain caregiver attention or escape instructional demands via their problem behavior. Behavioral interventions built upon this framework comprise the current standard of psychological care. These interventions typically involve teaching or otherwise promoting appropriate, alternative behaviors that produce identical or similar reinforcers as the problem behavior, to displace the problem behavior. Numerous studies have validated the effectiveness of these interventions under initial conditions, but others have revealed that their therapeutic effects sometimes wane as the ratio of responses to reinforcers is increased (or "thinned") to make the interventions practical in natural environments (e.g., classrooms). We previously proposed that principles from the field of behavioral economics, including stimulus substitutability and demand elasticity, can help to determine the conditions under which behavioral interventions may be expected to maintain their effects across changes in intervention schedules. In the initial budget period, we conducted investigations that demonstrated that a) the choice behavior of children with IDD and behavior disorders is systematically sensitive to behavioral economic manipulations involving stimulus substitutability and demand elasticity, and b) behavioral interventions based on these principles can often produce clinical effects that are more durable than what is often prescribed under the current standard of care. In the current proposal, we again adopt a translational approach to extend our analysis of behavioral economic principles, and their relevance to problem behavior, through both laboratory and clinical investigations. Six studies are proposed that a) further explore concepts of substitutability and demand elasticity to enhance treatment effects, b) employ concepts related to open vs. closed economies to both understand the influence of extraneous sources of reinforcement on response allocation and decrease motivation for problem behavior, and c) employ concepts related to "penalty" and "interest" to model how response allocation can be shifted away from problem behavior and towards appropriate behavior. PUBLIC HEALTH RELEVANCE: The current investigation aims to use concepts and principles of behavioral economics to enhance the practicality, durability, and efficacy of interventions for the severe behavior disorders of children with developmental disabilities.